Sodium lactate and method of manufacture



Patented Jan. 1 0, 1939 UNITED STATES PATENT OFFICE SODIUM LACTATE AND METHOD OF MANUFACTURE James F. Walsh, Chicago, Ill., assignor to American Maize-Products Company, a corporation of Maine No Drawing. Application October 25, 1937, Serial No. 170,765

2 Claims. (Cl. 260-535) My invention relates to the production of so- In the above described conventional process of dium lactate and more particularly to a substanmanufacturing sodium lactate it is to be noted tially colorless and odorless sodium lactate and that the sodium lactate is prepared first in a low its process of manufacture. concentration and then concentrated to the de- Sodium lactate produced by the usual procesired strength. During this concentration the 5 dure from fermentation liquors results in a prodimpurities contained in the weak sodium lactate, uct that has considerable color and an undesirsuch as, for example, calcium lactate and sodium able butyric acid odor which render the product sulphate, are also concentrated and form a satunfit for certain intended purposes, such as, use urated or supersaturated solution. Consequentas a softener in papers and textiles. In the usual ly, the sodium lactate prepared in this manner 10 procedure, sodium lactate is produced by decomis subject to the disadvantage of the impurities posing calcium lactate liquor with sodium carcrystallizing out on standing, thereby rendering bonate to form sodium lactate. This process the product hazy. briefly consists of the following steps: The solubilities of such salts as sodium sul- First, a carbohydrate material, preferably a phate and calcium lactate are extremely low in 15 sugar, is fermented with a suitable bacillus to concentrated sodium lactate solutions of over 50 produce lactic acid. The fermentation is carried per cent, whereas they are quite soluble in the out in the presence of a nutrient and an antiweaker sodium lactate liquors. In the usual acid such as calcium carbonate. The function of process, sodium lactate is formed in the weak the anti-acid is to continuously adjust the acidity liquor state and then concentrated to the desired 0 to the proper pH value during the fermentation strength. 'During the concentration and especycle, in which lactic acid is first produced by cially in the upper range, the solubilities of these the fermenting bacillus. This lactic acid reacts salts, calcium lactate and sodium sulphate, dewith the calcium carbonate to form calcium laccrease quite rapidly and the sodium lactate betate. At the end of the fermentation, that is comes a supersaturated solution of these salts. 25 when practically all of the carbohydrates or If the original concentrations of the salts are sugar have been utilized by the bacillus, there within the usual range and if the concentration remains a mixture of calcium lactate, a small of sodium lactate is Well over 50 per cent, preamount of free lactic acid, excess unreacted calcipitation of calcium lactate and sodium sulphate cium carbonate, and the non-utilized portion of usually occurs. 30 the nutrient used. This crystallization trouble is avoided in my In the next operation commonly referred to as p p d p s since the sodium a at s p othe killing step, the active organism i. e. bacilli, duced directly to the desired strength and no are killed by heating and all of the lactic acid concentration is necessary. Also, the amount of radicals are converted into their calcium salts, calcium lactate and sodium sulphate is minimized 35 i. e. calcium lactate. This is accomplished by by careful adjustments in the preparation of the heating the fermented liquor at about 180 F. or purified edible lactic acid, and also as calcium higher with sufiicient lime to give the mixture a sulphate precipitates during the concentration of pH of 10 to 12, usually a pH of 11. The resultthe acid. Finally during the neutralization of ing calcium lactate liquor is then separated by the concentrated acid with alkali, an excess of 40 filtration from the insoluble matter present. alkali is used to throw out the traces of metals The calcium lactate liquor at this stage has which may still remain.

usually a dark, reddish brown color, which can An object of my invention is to provide a methbe partly reduced by bleaching with a vegetable ed and means for producing sodium lactate that carbon. Either the bleached or unbleached is substantially colorless and odorless. 45

liquor is then converted to sodium lactate by re- In accordance with my present invention, the

acting the liquor with sodium carbonate formdesired sodium lactate, which is substantially ing the insoluble salt, calcium carbonate. The water white and has no undesirable odor, is obinsoluble calcium carbonate is separated from tained by first purifying and concentrating the 5 the alkaline sodium lactate liquor by filtering and raw materials or ingredients and then reacting the pH of the filtered soldium lactate is then the purified concentrated ingredients to form the adjusted to the proper value by adding a suitable sodium lactate product of desired strength and acid. The sodium lactate without further chempurity. This procedure avoids crystallization of ical treatment is concentrated to the desired conimpurities in the final product since the sodium centration, usually 50% sodium lactate. lactate formed does not have to be concentrated. on

The improved product of my invention may be obtained by reacting previously purified and concentrated, substantially colorless, lactic acid with concentrated sodium hydroxide, to form immediately a concentrated sodium lactate solution having the desired properties. The concentration of sodium lactate thus formed is controlled by the concentration of the purified lactic acid and'the sodium hydroxide used. The concentrated sodium lactate is filtered and bleached if necessary with a suitable bleaching agent, such as, for example, vegetable carbon. The final product resulting from this treatment is water white and practically odorless.

As above suggested, the usual undesirable properties of the lactic acid, such as, for example, color, odor, and metal constituents, are removed before the lactic acid is reacted with the sodium hydroxide. If the metals normallv contained in the lactic acid are not removed, they will remain as highly colored substances in the final sodium lactic product; An example 'of these metal impurities is iron lactate, which has a decided yellowcolor. In general, the metallic salts, such as, for example, copper and iron salts, if permitted to remain in the sodium lactate solution are slowly reduced and gradually precipitated as a colloidal haze in the sodium lactate solution, imparting to the latter undesirable physical and chemical properties. The purified lactic acid used in the process of my invention is previously treated to remove all of the undesirable metals and other I impurities. The usual undesirable odor in the sodium lactate, which is caused by the presence of sodium salts of volatile acids,

particularly the sodium salts of butyric acid, is

avoided by vacuum treatment of the lactic acid used.

When the concentrated lactic acid is reacted with the concentrated sodium hydroxide to form sodium lactate of the desired strength in accordance with this invention, a considerable amount of-heat is developed. If the heat so developed is permitted to raise the temperature of the reacting. materials to boiling, an appreciable amount of color will be. developed. In my proposed process, however, this color formation is minimized by controllingthe temperature of the reaction so that it. remains below approximately 160 F. This cooling efiect is accomplished by means of "any suitable form of cooling surface or coils and also by controlling the rate of the addition of sodium hydroxide to. the lactic acid.

In accordance with one specific but non-limiting embodiment of my invention, the desired "sodium lactate product of this invention may be produced as follows:

Lactic acid in the form known as edible lactic acid is concentrated under vacuum up to a high strength whereby butyric. acid and other odorous volatile acids having a higher vapor pressure than lactic acid are removed.- Then to approvimately 3000 pounds of this edible lactic acid of approximately 70 percent strength is added 1900 pounds of 50 Baum sodium hydroxide. The reaction caused by these two materials produces sodiumlactate having a concentration of approximately 50 to 53 per cent. When the reacting materials are used in this proportion the sodium lactate produced thereby contains a slight excess of sodium hydroxide. That is, the sodium lactate solution has a pH of 8 to 9. This alkalinity, I have found, effects maximum removal of aluminum, iron, and other metals. The sodium lactate solution is then filtered to remove the metallic hydroxides that have been precipitated and the filtered solution is bleached with about 50 pounds of vegetable carbon.

The sodium hydroxide is added to the lactic acid carefully and slowly and some suitable cooling means such as cold water coils are used to control the heat so that the temperature of the reacting mixture-is-kept down to a relatively low value, such as 100 F. to 160 F. At the end of this reaction between the sodium hydroxide and the lactic acid the pH of the resulting solution may be adjusted to about 6.8 or to any desired pH suitable for the intended use of the sodium lactate product.

It is to be understood that various modifications and changes may be made in the process as described hereinabove without departing from the scope of my invention. For example, the sodium hydroxide used may bev in either concentrated liquid or in flake form, or a combination 'of both forms may be used.

Some of the novel features of my invention .are defined the appended claims.

I claim:

1. A process of producing substantially colorless and odorless sodium lactate comprising reacting concentrated lactic acid with an excess of concentrated sodium hydroxide to produce concentrated sodium lactate of over 50% strength, the temperature of the reacting mixture of lactic acid and sodium hydroxide being maintained below about 160 F. by cooling to prevent discoloration of the sodium lactate, said sodium' hydroxide being usedin sufllcient excess to give the resulting sodium lactate solution a pH of aboutv 8-9, and thereby effect maximum precipitation of aluminum and iron as metallic hydroxides, removing said hydroxides, adjusting the pH of the solution to an acid pH and bleaching the resulting acid sodium lactate solution.

2, A process of producing substantially colorless and odorless sodium lactate comprising reacting concentrated lactic acid with an excess of concentrated sodium hydroxide to produce concentrated sodium lactate of over 50% strength, the temperature of the reacting mixture of lactic acid and sodium hydroxide being maintained below about 160 F. bycooling to prevent discoloration of the sodium lactate, said sodium hydroxide being used in sufiicient excess to give the resulting sodium lactate. solution a. pH of about 8-9,

and thereby effectv maximum precipitation of aluminum and iron asmetallic hydroxides, removing said hydroxides, adjusting the pH of the solution to about 6.8 and bleaching the resulting acidsodium lactate solution with vegetable carbon.

JAMES. F. WALSH. 

